Adjusting the LCD Screen Display Size

Can somebody help me to get through with this...

i have my old laptop P133Mhz AST, my problem is, everytime I log in Win98SE, the screen display seems to be too small. It does not maximize the size of the actual screen. Is there anyway that i can restore the original size of the screen display??? this bothers me a lot and i hope this time someone could share his idea to solve this....
many thanks...